This invention relates generally to an efficient ligand-accelerated Ullmann coupling reaction of anilines with azoles. The coupling products are useful for preparing factor Xa inhibitors.
Factor Xa inhibitors like those of Formulas Ia and Ib shown below: 
are currently being investigated as potential drug candidates. As a result, large quantities of these compounds are needed to satisfy clinical demands.
WO98/57951 describes of the synthesis of compounds of formula Ia and Ib as shown below. 
In procedure Ia, the resulting imidazolyl-aniline is coupled with 1-(3-cyano-4-fluorophenyl)-3-trifluoromethyl-5-pyrazole carboxylic acid and the resulting intermediate is then converted to the final product. Procedure Ia is problematic in that it provides isomers of the imidazolyl-nitrobenzene. In procedure Ib, the resulting imidazolyl-aniline is coupled with 1-(3xe2x80x2-aminobenzisoxozol-5-yl)-3-trifluoromethyl-5-pyrazolecarboxylic acid to provide the final product. Procedure Ib is problematic in that it only provides a 48.5% yield of the imidazolyl-aniline intermediate starting from the bromo-fluoroaniline.
Many different kinds of aryl halides have been used as substrates for the Ullmann-type amination reaction. This most straightforward route to N-(amino)arylimodazoles involves the direct formation of the aromatic carbon-nitrogen bond under the catalysis of a copper(I) salt without protection of the aromatic amino functionality. However, there is almost no precedent to directly employ unprotected aniline derivatives as coupling partners. The free NH2 functionality on the aryl halides is reported to have a deleterious effect (35-50% yields of unprotected aniline substrates vs 75-100% yields of non-aniline substrates or protected aniline substrates) on the Ullmann coupling reaction (J. Chem. Soc. (C) 1969, 312). One report revealed that direct coupling of 4-iodoaniline with imidazole under the Cu(I)-catalyzed condition afforded the desired N-(4-amino)arylimidazole only in 37% yield (J. Med. Chem. 1988, 31, 2136). Another report observed that no coupling products was obtained when unprotected 2-fluoro-4-iodoaniline was exposed to the Ullmann ether synthesis (Synthesis, 1998, 1599). In that report, the authors also found that protection of the aromatic amino group to amide or carbamate before being subjected to the Ullmann coupling reaction resulted only in the cleavage of the protection group without formation of any desired coupling product. Therefore, a hydrolytically stable 2,5-dimethylpyrrole derivative of that aniline substrate was prepared. Obviously, two more steps (protection and deprotection) is added to the synthetic sequence in order to form the aromatic carbon-nitrogen or carbon-oxygen bond when the halogenated aniline is used as the coupling substrate.
It can be seen that preparation of factor Xa inhibitors, specifically preparation of azolyl-aniline intermediates useful therein, is difficult. Thus, it is desirable to find efficient syntheses azolyl-anilines that are useful in making factor Xa inhibitors of compounds like those of formulas Ia and Ib.
Accordingly, one object of the present invention is to provide novel processes for preparing azolyl-anilines using a ligand-mediated Ullmann coupling reaction.
These and other objects, which will become apparent during the following detailed description, have been achieved by the inventors"" discovery that imidazolyl-anilines like those shown below (formulas IIa and IIb): 
can be prepared by ligand-accelerated Ullmann coupling of non-protected, halo-substituted anilines and azoles. This is the first time an Ullmann coupling of an aniline has been shown to work efficiently without protection of the aniline nitrogen.
The present invention demonstrates that Cu(I)-catalyzed coupling of iodoanilines to imidazoles is accelerated by a group of hydrolytically stable ligands known to coordinate Cu(I) catalyst. The ligands, preferably the alkyl and aryl bidentate nitrogen and oxygen containing compounds, used in an equimolar amount with respect to Cu(I) catalyst, are found to produce the significant rate acceleration for the coupling reaction. The reaction temperature (100-130xc2x0 C. vs  greater than 150xc2x0 C.) is significantly lower and the reaction time (4-6 h vs 16-24 h) is significantly shorter with this ligand-accelerated protocol. And also, the coupling yield is improved with the addition of the ligand.
The present method is the first reported actual ligand-accelerated Cu(I)-catalyzed Ullmann coupling of the aryl halides to azoles, including imidazoles. Both Cu(I) salt and ligand used in this method are used in catalytical amounts (5-15%). In the previous reports, both Cu(I) catalyst and ligand were employed excessively (0.2 to 2.0 equivalents). In contrast to Buchwald""s report (Tetrahedron Lett. 1999, 40, 2657), which is the only reported ligands-accelerated Ullmann coupling of aryl halides to imidazoles so far, this method uses only one additive to be as the ligand to promote the reaction. Instead of the use of 10-fold excess of the ligand with respect to the Cu(I) catalyst (Tetrahedron Lett. 1999, 40, 2657), the method detailed of the present invention employs the equimolar amount of ligand with respect to the copper catalyst.
In an embodiment, the present invention provides a novel process for making a compound of Formula III: 
comprising: contacting an aniline of Formula IV with an azole of Formula V in the presence of Cu(I)X1 and a bidentate ligand: 
wherein:
in Formula IV, from 0-1 of the carbon atoms are replaced with N;
in Formula V, from 0-3 of the carbon atoms are replaced with N;
alternatively, the compound of Formula V is benzo-fused and 0-2 of the carbon atoms of the five-membered ring are replaced with N;
X1 is selected from Cl, Br, I, and SCN;
X2 is selected from Br or I;
R1 is selected from H, Cl, F, Br, I, C1-4 alkyl, C1-4 alkoxy, C1-4 alkylene-Oxe2x80x94C1-4 alkyl, NH2, NH(C1-4 alkyl), N(C1-4 alkyl)2, C1-4 alkylene-NH2, C1-4 alkylene-NH(C1-4 alkyl), C1-4 alkylene-N(C1-4 alkyl)2, C3-10 carbocycle substituted with 0-2 R3, 5-6 membered heterocycle comprising carbon atoms and 1-4 heteroatoms selected from N, O, and S and substituted with 0-2 R3;
R2 is selected from H, Cl, F, Br, I, C1-4 alkyl, C1-4 alkoxy, C1-4 alkylene-Oxe2x80x94C1-4 alkyl, NH2, NH(C1-4 alkyl), N(C1-4 alkyl)2, C1-4 alkylene-NH2, C1-4 alkylene-NH(C1-4 alkyl), C1-4 alkylene-N(C1-4 alkyl)2, C3-10 carbocycle substituted with 0-2 R3, 5-6 membered heterocycle comprising carbon atoms and 1-4 heteroatoms selected from N, O, and S and substituted with 0-2 R3;
R3 is selected from Cl, F, Br, I, C1-4 alkyl, C1-4 alkoxy, C1-4 alkylene-Oxe2x80x94C1-4 alkyl, NH2, NH(C1-4 alkyl), N(C1-4 alkyl)2, C1-4 alkylene-NH2, C1-4 alkylene-NH(C1-4 alkyl), C1-4 alkylene-N(C1-4 alkyl)2, and NO2;
r is 1 or 2; and,
the bidentate ligand is a hydrolytically stabile ligand that is known to ligate with Cu(I) and comprises two heteroatoms selected from N and O.
In a preferred embodiment, the bidentate ligand is selected from tetramethylethylenediamine (TMED), 2,2xe2x80x2-dipyridyl (DPD), 8-hydroxyquinoline (HQL), and 1,10-phenanthroline (PNT) and from 0.01-0.20 equivalents are present, based on the molar amount of aniline present.
In another preferred embodiment, the bidentate ligand is 8-hydroxyquinoline (HQL) or 1,10-phenanthroline (PNT) and from 0.05-0.15 equivalents are present.
In another preferred embodiment, the bidentate ligand is 8-hydroxyquinoline (HQL) and from 0.05-0.15 equivalents are present.
In another preferred embodiment, the bidentate ligand is 1,10-phenanthroline (PNT) and from 0.05-0.15 equivalents are present.
In another preferred embodiment, from 0.01-0.20 equivalents of Cu(I)X1 are present, based on the molar amount of aniline present.
In another preferred embodiment, from 0.05-0.15 equivalents of Cu(I)X1 are present.
In another preferred embodiment, 0.05 equivalents of Cu(I)X1 are present.
In another preferred embodiment, 0.15 equivalents of Cu(I)X1 are present.
In another preferred embodiment, the contacting is performed in the presence of from 1.0-2.0 molar equivalents of base, based on the molar amount of aniline present.
In another preferred embodiment, the contacting is performed in the presence of from 1.0-1.2 equivalents of K2CO3.
In another preferred embodiment, the contacting is performed in the presence of 1.05 equivalents of K2CO3.
In another preferred embodiment, from 1-1.5 molar equivalents of azole are used, based on the molar amount of aniline present.
In another preferred embodiment, from 1.1-1.3, molar equivalents of azole are used, based on the molar amount of aniline present.
In another preferred embodiment, from 1.2 molar equivalents of azole are used, based on the molar amount of aniline present.
In another preferred embodiment, the contacting is performed in a polar solvent.
In another preferred embodiment, the contacting is performed in a polar, aprotic solvent.
In another preferred embodiment, the contacting is performed in DMSO.
In another preferred embodiment, the contacting is performed at a temperature of from 100xc2x0 C. to reflux of the solvent and the reaction is run from 4 to 24 hours.
In another preferred embodiment, the contacting is performed at a temperature of from 110 to 140xc2x0 C. and from 6 to 15 hours.
In another preferred embodiment, the contacting is performed at a temperature of from 120 to 130xc2x0 C.
In another preferred embodiment, X1 is I or SCN.
In another preferred embodiment, X1 is I.
In another preferred embodiment, X1 is SCN.
In another preferred embodiment, Formula V is an imidazole;
alternatively, the compound of Formula V is a benzo-fused imidazole;
R1 is selected from H, Cl, F, methyl, ethyl, i-propyl, methoxy and, methoxymethylene;
R2 is selected from H, methyl, i-propyl, NH2, CH2NH2, CH2N(CH3)2, and phenyl; and,
r is1.
In another preferred embodiment, the compound of Formula IV is selected from: 
and, the compound of Formula V is selected from: 
In another preferred embodiment, the compound of Formula IV is: 
and, the compound of Formula V is selected from: 
In another preferred embodiment, the compound of Formula V is: 
In another preferred embodiment, the compound of Formula V is: 
As used herein, the following terms and expressions have the indicated meanings. It will be appreciated that the compounds of the present invention contain an asymmetrically substituted carbon atom, and may be isolated in optically active or racemic forms. It is well known in the art how to prepare optically active forms, such as by resolution of racemic forms or by synthesis, from optically active starting materials. All chiral, diastereomeric, racemic forms and all geometric isomeric forms of a structure are intended, unless the specific stereochemistry or isomer form is specifically indicated.
The processes of the present invention are contemplated to be practiced on at least a multigram scale, kilogram scale, multikilogram scale, or industrial scale. Multigram scale, as used herein, is preferably the scale wherein at least one starting material is present in 10 grams or more, more preferably at least 50 grams or more, even more preferably at least 100 grams or more. Multikilogram scale, as used herein, is intended to mean the scale wherein more than one kilogram of at least one starting material is used. Industrial scale as used herein is intended to mean a scale which is other than a laboratory scale and which is sufficient to supply product sufficient for either clinical tests or distribution to consumers.
The term xe2x80x9csubstituted,xe2x80x9d as used herein, means that any one or more hydrogens on the designated atom is replaced with a selection from the indicated group, provided that the designated atom""s normal valency is not exceeded, and that the substitution results in a stable compound. When a substituent is keto (i.e., xe2x95x90O), then 2 hydrogens on the atom are replaced. Keto substituents are not present on aromatic moieties. When a ring system (e.g., carbocyclic or heterocyclic) is said to be substituted with a carbonyl group or a double bond, it is intended that the carbonyl group or double bond be part (i.e., within) of the ring.
The present invention is intended to include all isotopes of atoms occurring in the present compounds. Isotopes include those atoms having the same atomic number but different mass numbers. By way of general example and without limitation, isotopes of hydrogen include tritium and deuterium. Isotopes of carbon include C-13 and C-14.
When any variable (e.g., R1) occurs more than one time in any constituent or formula for a compound, its definition at each occurrence is independent of its definition at every other occurrence. Thus, for example, if a group is shown to be substituted with 0-2 R1, then said group may optionally be substituted with up to two R1 groups and R1 at each occurrence is selected independently from the definition of R1. Also, combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.
When a bond to a substituent is shown to cross a bond connecting two atoms in a ring, then such substituent may be bonded to any atom on the ring. When a substituent is listed without indicating the atom via which such substituent is bonded to the rest of the compound of a given formula, then such substituent may be bonded via any atom in such substituent. Combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.
As used herein, xe2x80x9calkylxe2x80x9d or xe2x80x9calkylenexe2x80x9d is intended to include both branched and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms. C1-10 alkyl (or alkylene), is intended to include C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10 alkyl groups. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, and s-pentyl. xe2x80x9cHaloalkylxe2x80x9d is intended to include both branched and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms, substituted with 1 or more halogen (for example xe2x80x94CvFw where v=1 to 3 and w=1 to (2v+1)). Examples of haloalkyl include, but are not limited to, trifluoromethyl, trichloromethyl, pentafluoroethyl, and pentachloroethyl. xe2x80x9cAlkoxyxe2x80x9d represents an alkyl group as defined above with the indicated number of carbon atoms attached through an oxygen bridge. C1-10 alkoxy, is intended to include C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10 alkoxy groups. Examples of alkoxy include, but are not limited to, methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, s-butoxy, t-butoxy, n-pentoxy, and s-pentoxy. xe2x80x9cCycloalkylxe2x80x9d is intended to include saturated ring groups, such as cyclopropyl, cyclobutyl, or cyclopentyl. C3-7 cycloalkyl, is intended to include C3, C4, C5, C6, and C7 cycloalkyl groups. xe2x80x9cAlkenylxe2x80x9d or xe2x80x9calkenylenexe2x80x9d is intended to include hydrocarbon chains of either a straight or branched configuration and one or more unsaturated carbon-carbon bonds that may occur in any stable point along the chain, such as ethenyl and propenyl. C2-10 alkenyl (or alkenylene), is intended to include C2, C3, C4, C5, C6, C7, C8, C9, and C10 alkenyl groups. xe2x80x9cAlkynylxe2x80x9d or xe2x80x9calkynylenexe2x80x9d is intended to include hydrocarbon chains of either a straight or branched configuration and one or more triple carbon-carbon bonds that may occur in any stable point along the chain, such as ethynyl and propynyl. C2-10 alkynyl (or alkynylene), is intended to include C2, C3, C4, C5, C6, C7, C8, C9, and C10 alkynyl groups.
As used herein, xe2x80x9ccarbocyclexe2x80x9d or xe2x80x9ccarbocyclic groupxe2x80x9d is intended to mean any stable 3, 4, 5, 6, or 7-membered monocyclic or bicyclic or 7, 8, 9, 10, 11, 12, or 13-membered bicyclic or tricyclic, any of which may be saturated, partially unsaturated, or aromatic. Examples of such carbocycles include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, cyclooctyl, [3.3.0]bicyclooctane, [4.3.0]bicyclononane, [4.4.0]bicyclodecane, [2.2.2]bicyclooctane, fluorenyl, phenyl, naphthyl, indanyl, adamantyl, and tetrahydronaphthyl.
As used herein, the term xe2x80x9cheterocyclexe2x80x9d or xe2x80x9cheterocyclic groupxe2x80x9d is intended to mean a stable 5, 6, or 7-membered monocyclic or bicyclic or 7, 8, 9, or 10-membered bicyclic heterocyclic ring which is saturated, partially unsaturated or unsaturated (aromatic), and which consists of carbon atoms and 1, 2, 3, or 4 heteroatoms independently selected from the group consisting of N, NH, O and S and including any bicyclic group in which any of the above-defined heterocyclic rings is fused to a benzene ring. The nitrogen and sulfur heteroatoms may optionally be oxidized. The heterocyclic ring may be attached to its pendant group at any heteroatom or carbon atom that results in a stable structure. The heterocyclic rings described herein may be substituted on carbon or on a nitrogen atom if the resulting compound is stable. A nitrogen in the heterocycle may optionally be quaternized. It is preferred that when the total number of S and O atoms in the heterocycle exceeds 1, then these heteroatoms are not adjacent to one another. It is preferred that the total number of S and O atoms in the heterocycle is not more than 1. As used herein, the term xe2x80x9caromatic heterocyclic groupxe2x80x9d or xe2x80x9cheteroarylxe2x80x9d is intended to mean a stable 5, 6, or 7-membered monocyclic or bicyclic or 7, 8, 9, or 10-membered bicyclic heterocyclic aromatic ring which consists of carbon atoms and 1, 2, 3, or 4 heteroatoms independently selected from the group consisting of N, NH, O and S. It is to be noted that total number of S and O atoms in the aromatic heterocycle is not more than 1.
Examples of heterocycles include, but are not limited to, acridinyl, azocinyl, benzimidazolyl, benzofuranyl, benzothiofuranyl, benzothiophenyl, benzoxazolyl, benzoxazolinyl, benzthiazolyl, benztriazolyl, benztetrazolyl, benzisoxazolyl, benzisothiazolyl, benzimidazolinyl, carbazolyl, 4aH-carbazolyl, carbolinyl, chromanyl, chromenyl, cinnolinyl, decahydroquinolinyl, 2H,6H-1,5,2-dithiazinyl, dihydrofuro[2,3-b]tetrahydrofuran, furanyl, furazanyl, imidazolidinyl, imidazolinyl, imidazolyl, 1H-indazolyl, indolenyl, indolinyl, indolizinyl, indolyl, 3H-indolyl, isatinoyl, isobenzofuranyl, isochromanyl, isoindazolyl, isoindolinyl, isoindolyl, isoquinolinyl, isothiazolyl, isoxazolyl, methylenedioxyphenyl, morpholinyl, naphthyridinyl, octahydroisoquinolinyl, oxadiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl, oxazolidinyl, oxazolyl, oxindolyl, pyrimidinyl, phenanthridinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, phenoxathinyl, phenoxazinyl, phthalazinyl, piperazinyl, piperidinyl, piperidonyl, 4-piperidonyl, piperonyl, pteridinyl, purinyl, pyranyl, pyrazinyl, pyrazolidinyl, pyrazolinyl, pyrazolyl, pyridazinyl, pyridooxazole, pyridoimidazole, pyridothiazole, pyridinyl, pyridyl, pyrimidinyl, pyrrolidinyl, pyrrolinyl, 2H-pyrrolyl, pyrrolyl, quinazolinyl, quinolinyl, 4H-quinolizinyl, quinoxalinyl, quinuclidinyl, tetrahydrofuranyl, tetrahydroisoquinolinyl, tetrahydroquinolinyl, tetrazolyl, 6H-1,2,5-thiadiazinyl, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, thianthrenyl, thiazolyl, thienyl, thienothiazolyl, thienooxazolyl, thienoimidazolyl, thiophenyl, triazinyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,5-triazolyl, 1,3,4-triazolyl, and xanthenyl. Also included are fused ring and spiro compounds containing, for example, the above heterocycles.
The reactions of the synthetic methods claimed herein are preferably carried out in the presence of a suitable base, said suitable base being any of a variety of bases, the presence of which in the reaction facilitates the synthesis of the desired product. Suitable bases may be selected by one of skill in the art of organic synthesis. Suitable bases include, but are not limited to, inorganic bases such as alkali metal, alkali earth metal, thallium, and ammonium hydroxides, alkoxides, phosphates, and carbonates, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, thallium hydroxide, thallium carbonate, tetra-n-butylammonium carbonate, and ammonium hydroxide.
The reactions of the synthetic methods claimed herein are carried out in suitable solvents which may be readily selected by one of skill in the art of organic synthesis, the suitable solvents generally being any solvent which is substantially non-reactive with the starting materials (reactants), the intermediates, or products at the temperatures at which the reactions are carried out, i.e., temperatures which may range from the solvent""s freezing temperature to the solvent""s boiling temperature. A given reaction may be carried out in one solvent or a mixture of more than one solvent. Depending on the particular reaction step, suitable solvents for a particular reaction step may be selected.
Preferably, the contacting is performed in a suitable polar solvent. Suitable polar solvents include, but are not limited to, ether and aprotic solvents.
Suitable ether solvents include: dimethoxymethane, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, furan, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, or t-butyl methyl ether.
Suitable aprotic solvents may include, by way of example and without limitation, tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU), 1,3-dimethyl-2-imidazolidinone (DMI), N-methylpyrrolidinone (NMP), formamide, N-methylacetamide, N-methylformamide, acetonitrile, dimethyl sulfoxide, propionitrile, ethyl formate, methyl acetate, hexachloroacetone, acetone, ethyl methyl ketone, ethyl acetate, sulfolane, N,N-dimethylpropionamide, tetramethylurea, nitromethane, nitrobenzene, or hexamethylphosphoramide.
The processes of the present invention can be practiced in a number of ways depending on the solvent, base, chiral moderator, and temperature chosen. As one of ordinary skill in the art of organic synthesis recognizes, the time for reaction to run to completion as well as yield and enantiomeric excess will be dependent upon all of the variables selected.
Aniline Substrate
Under the same reaction conditions, the coupling reaction with iodoanilines as the substrates was found to be faster than that with the corresponding bromoanilines as the substrates. This reactivity difference between iodoanilines and bromoanilines is found to be even greater without ligand acceleration. Without the ligand acceleration, the coupling of bromoanilines to azoles takes 24 to 48 hours to completion while the coupling of iodoanilines to azoles is complete in 10-20 hours at the same reaction temperature (120-130xc2x0 C.). However, the coupling reaction of either iodoanilines or bromoanilines to azoles is significantly accelerated when an equimolar amount of ligand, such as 8-hydroxyquinoline, is employed. This ligand-acceleration is especially remarkable for the bromoanilines. With the addition of the ligand, the coupling reaction of bromoanilines to imidazoles reaches completion in 6 to 8 hours at the same reaction temperature (120-130xc2x0 C.). Therefore, with this ligand acceleration, both iodoanilines and bromoanilines are suitable coupling substrates, even though the former substrate provides the faster reaction rate. The preferred substrate is an iodoaniline.
Cu(I) Catalyst
The Cu(I) catalyst is preferably a Cu(I) salt selected from CuCl, CuBr, CuBr-SMe2, CuSCN, CuI, and CuOTf. More preferably, the Cu(I) catalyst is selected from CuCl, CuSCN, and CuI. A more preferred Cu(I) catalyst is CuSCN. Another more preferred Cu(I) catalyst is CuI.
The amount of Cu(I) catalyst used depends on the selected starting materials and reaction conditions. Preferably, from 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, to 0.20 equivalents of Cu(I)X are present. More preferably, from 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, to 0.15 equivalents of Cu(I)X are present. An even more preferred amount of catalyst is 0.05 equivalents. Another even more preferred amount of catalyst is 0.15 equivalents. For large scale reactions, it is preferred that about 0.05 equivalents of CuI is used.
Ligand
Rate accelerations have been reported in the industrially important Ullmann ether condensation reaction. Several different kinds of organic molecules, such as alkyl formates or simple alkyl carboxylates and alkyl and aryl monodentate and bidentate nitrogen/oxygen containing compounds, were found to be able to affect the catalyst (copper(I) salt) competency in the Ullmann condensation reactions. Those compounds are found to possess the ability to ligate the copper(I) catalyst. However, the Ullmann coupling reaction is normally conducted under the basic condition, the ligand used in this reaction, therefore, must be stable enough to coordinate the Cu(I) catalyst.
A bidentate ligand that is a hydrolytically stabile is useful in the present invention. The ligand should ligate with Cu(I) and comprises two heteroatoms selected from N and O. Preferably, the bidentate ligand is selected from tetramethylethylenediamine (TMED), 2,2xe2x80x2-dipyridyl (DPD), 8-hydroxyquinoline (HQL), and 1,10-phenanthroline (PNT). More preferably, the bidentate ligand is 8-hydroxyquinoline (HQL) or 1,10-phenanthroline (PNT). An even more preferred bidentate ligand is 8-hydroxyquinoline (HQL). An even more preferred bidentate ligand is 1,10-phenanthroline (PNT).
The amount of bidendate ligand present should be approximately equivalent to the amount of Cu(I) catalyst present. Thus, from 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, to 0.20 molar equivalents of bidentate ligand are present. More preferably, from 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, to 0.15 equivalents of bidentate ligand are present. An even more preferred amount of bidentate ligand is 0.05 equivalents. Another even more preferred amount of bidentate ligand is 0.15 equivalents. For large scale reactions, it is preferred that about 0.05 equivalents of CuI is used.
Base
In this Ullmann coupling of iodoanilines to azoles, a base is preferred to scavenge the in situ generated hydrogen iodide (or hydrogen bromide). Moreover, this base can also serve to deprotonate the azole to form the corresponding azole anion, which is a more reactive coupling partner. Preferably this base is inorganic and more preferably weak. K2CO3 and Cs2CO3 are preferred bases. Potassium carbonate is preferred when a polar, aprotic solvent is used. Cesium carbonate is preferred if a less polar organic solvent is used.
The amount of base is preferably 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, to 2.0 molar equivalents, more preferably 1.0 to 1.2 and even more preferably 1.05. In large scale reactions, it is preferable to use about 1.05 equivalents of K2CO3.
Mole Ratio of Aniline to Azole
The coupling reaction proceeds smoothly when the equal molar substrates are used. However, a significant amount of the unreacted iodoaniline is usually recovered. Therefore, it is preferable to use a slight excess amount of the azoles. The molar ratio of the aniline to azole is preferably 1, 1.1, 1.2, 1.3, 1.4, to 1.5. More preferably, the molar ratio is from 1.1, 1.2, to 1.3. Even more preferably, the molar ratio is about 1.2.
Solvent
Polar solvents can be used in the present invention. However, polar, aprotic solvents are preferred. DMSO is a preferred polar, aprotic solvent. Under the thermal condition, this polar, aprotic solvent promotes the deprotonation of the azole by the inorganic, weak base (K2CO3) to its corresponding anion, which is proven to be the better coupling partner. A ethylene glycol derivatives, such as ethylene glycol monoalkyl ethers, are also suitable solvents for this coupling reaction. Even though these solvents did not give the better results for this coupling reaction comparing to DMSO, their free hydroxyl group does not interfere the azole coupling with iodoanilines. With DMSO as solvent, the reaction concentration is preferably from 0.8 to 1.0 M. When DMSO is used on large scale, the preferred concentration is 1.0 M.
Oxygen, particularly the dissolved oxygen in the solvent, was found to interfere the coupling reaction significantly. First, it deactivates the catalyst by oxidation of copper salt. Secondly, it could oxidize the iodoanilines. Therefore, this Ullmann coupling reaction is preferably conducted strictly under a nitrogen atmosphere.
Temperature and Reaction Time
The Ullmann coupling of iodoanilines to azoles is a thermally promoted reaction. Thus, it is preferable to run the coupling reaction under heat. Preferably, the contacting is performed at a temperature of from 100xc2x0 C. to reflux of the solvent and the reaction is run from 4 to 24 hours. More preferably, the contacting is performed at a temperature of from 110 to 140xc2x0 C. and from 6 to 15 hours. Even more preferably, the contacting is performed at a temperature of from 120 to 130xc2x0 C.
Workup
The work-up of the coupling reaction can be relatively difficult and time consuming. The desired coupling product is usually a hydrophilic material. Therefore, the amount of the aqueous solution used for quenching the reaction is preferably as small as possible and the organic solvent extraction process is repeated several times in order to get the good recovery of the product.
In a typical work-up process, a saturated NH4Cl aqueous solution or a 14% aqueous NH4OH solution is used to quench the reaction and to remove the Cu(I) catalyst by forming the water soluble copper complex. The aqueous solution is usually extracted with an organic solvent, such as ethyl acetate, several times. Approximately, 90-95% of the desired coupling product can be recovered from the reaction mixture. Activated carbon is employed, if necessary, to decolorize the organic extracts. Pale-yellow to off-white crystals are usually obtained as the crude product in good to excellent yield (65-85%) and quality ( greater than 95% pure). The better quality of the material ( greater than 99% pure) can be obtained from one simple recrystallization of the crude material from an organic solvent or an organic solvent system, such as ethyl acetate and heptane.
Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments that are given for illustration of the invention and are not intended to be limiting thereof.